I'll put it this way: Colt ARs specifically had far better production quality and processes than anyone else for decades and ad far as I can tell it's continued. The trigger pins were center ground and held within less than .001" for years. The shop finally burned up their equipment and they went to centerless, but they're still stupid precise. Most places chop them from drill rod and they vary, or are bent.
The carriers I've seen were amazing. Surfaces were honed exactly right with amazing surface finishes. Most that I checked would run 8-12ra, where the spec is 32. Most modern carriers are 45-50ra and it matters. Gas rings dont last as long, and the gas seal often sucks which leads to malfunctions. The tail hole? ****, most shops don't even check them and it's critical.
The cam slots were revised on mil spec carriers in the 2000s because no one but Colt could make them right. They doubled the tolerance from .003 to .006 because FN told the government that it didn't matter and that "it's not possible in production", yet every colt carrier I ever checked was perfect. The increase in tolerance has resulted in accelerated wear to uppers.
Same with the chrome. Getting it right on the gas keys, carrier and barrel isn't easy. One of the super big names in the barrel making world is one of the lowest quality products on the market, btw. Even after getting a contract to supply m4s.
This is all based on personal experience too. Not hearsay. Colt does know what they're doing and they're forced to pay higher wages to boot. As a result their prices are higher, and not necessarily just because of the better quality but because of their legacy commitments to pensions and also because labor simply costs more where they are.
Lots of budget AR shops might as well be El Salvadoran sweat shops, and the quality is commensurate with that.
